Method and apparatus for enhanced short message service

ABSTRACT

The present invention relates generally to mobile communication systems, methods and apparatus for transmitting messages from an originating party to a receiving mobile station, and transmitting short message service (SMS) messages from an originating party to a receiving mobile station in a mobile communication system. Briefly, the present invention solves a problem by transmitting both a message and a validity period ( 401 ) associated with the message from the message center to the receiving mobile station. By transmitting both a message and a validity period ( 401 ), associated with the message, where the validity period ( 401 ) specified by the sender of the message, the receiving mobile station can use the validity period ( 610 ) information when making decisions on how to process the received message.

This application claims the benefit of the filing date of Swedish patentapplication number 0002766-4 filed on Jul. 21, 2000 and PCT applicationnumber PCT/SE01/01315 filed on Jun. 8, 2001.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to mobile communication systems,methods and apparatus for transmitting messages from an originatingparty to a receiving mobile station, and specifically to transmittingshort message service (SMS) messages from an originating party to areceiving mobile station in a mobile communication system.

DESCRIPTION OF RELATED ART

Radiocommunication systems, such as cellular systems, support aplurality of different communication services. The most commonlyrecognized and widely used communication service relates to handlingvoice communications to and from the mobile stations of cellularsubscribers. Cellular systems may further support e.g. asynchronous datacommunications, facsimile communications and short message service(SMS). The short message service (SMS) provides for the transmission ofmessages having up to a limited number of alphanumeric characters to besent to a subscriber at his or her remote unit.

When sending SMS messages to and from a mobile station, a messagecenter, which stores and forwards the SMS messages, is used. It shouldbe noted that SMS messages can be sent from a computer connected to theInternet. Further an e-mail (electronic mail) can be sent to a mobilestation, but then it is converted to an SMS message.

When transmitting an SMS message to a receiving mobile station (MS),radio base stations (RBSs), and mobile switching centers (MSCs), arealso involved beside the message centers. The communication between theMSCs and message centers is handled by different network interfaces suchas TIA/EIA-41. The communication between MSC/RBS and mobile stations ishandled by different air interfaces such as TIA/EIA-136. For a cellularsystem conforming to TIA/EIA-136, the SMS message is transmitted betweenan MSC and a mobile station on a Digital Control Channel (DCCH) orDigital Traffic Channel (DTC) inside a layer 3 R-DATA message. The SMSmessage is encapsulated into a User Data Unit of a SMS SUBMIT messagefrom an originating party transmitting the message to the MSC andmessage center. The SMS message is encapsulated into a User Data Unit ofa SMS DELIVER message when submitted to the receiving mobile station,from the corresponding message center and MSC of the receiving mobilestation.

The sender of an SMS message could today specify a validity period ofthe message. This information is used by the message center to determinefor how long the message center should continue to try and forward themessage to the receiving mobile station, e.g. if the receiving mobilestation is switched off.

It is possible however that despite the message center managed to send aspecific message within the validity period, the validity period of themessage expires while the message is in the receiving mobile stationmemory before the receiver reads it.

SUMMARY OF THE INVENTION

The problem dealt with by the present invention is providing a moreflexible processing of messages at a receiving mobile station.

One exemplary scenario is that a message that has been delivered to thereceiving mobile station becomes overdue and still remains in thereceiver's mobile station memory. For someone that receives severalmessages a day, having useless messages stored in his/her mobile stationis inconvenient. It might result in that some important messages in thememory needs to be erased due to lack of space in the memory when a newmessage is received or that the new message is never saved. Therefore,important messages may never be saved or older interesting messages maybe deleted before they have been read.

Briefly, the present invention solves said problem by transmitting botha message and a validity period associated with the message from themessage center to the receiving mobile station.

By transmitting both a message and a validity period associated with themessage, where the validity period is specified by the sender of themessage, the receiving mobile station can use the validity periodinformation when making decisions on how to process the receivedmessage.

An object of the invention is to enable a more flexible way ofprocessing messages at a receiving mobile station.

Another object of the invention is to offer the receiver of a message achoice of determining how overdue messages should be processed.

An advantage of the present invention is enabling more flexibleprocessing of messages at a receiving mobile station.

A further advantage of the present invention is that the receiver of amessage has the choice of determining how overdue messages should beprocessed, thereby memory space in the mobile station could be used formore important messages.

Another advantage of the present invention is the possibility to use thevalidity period in a second memory, which could be an external memoryfrom the mobile station such as e.g. a digital calendar. Functions canbe included in the calendar as to sort messages after their validityperiod or to make the user of the calendar aware of an important messagebefore the validity period of the message has expired.

Still an advantage is that the invention makes it possible for themessage center to transmit the messages regardless of the contents inthe field validity period. Instead of as today when the message centeris deleting all overdue messages in the message center according to thevalidity period. Then the user of the receiving mobile station isincreasing his/her control of what to do with his/her messages. It canbe optional of course to let the message center delete overdue messagesaccording to the validity period or to transmit regardless, still themessages transmitted in time to the mobile station can be processed inaccordance with the preferences set by the user.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings andclaims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a mobile telecommunication systemincluding two mobile stations.

FIG. 2 is a block diagram illustrating layer 2 subchannels of thedigital control channel DCCH and the digital traffic channel DTC.

FIG. 3 is a signal diagram illustrating a message flow from a sendingmobile station to a receiving mobile station.

FIG. 4 is a schematic representation illustrating a transmissionprotocol when sending a SMS DELIVER message according to the invention.

FIG. 5 is a flow chart illustrating a message management solutiondependent on a validity period according to the invention.

FIG. 6 is a block diagram illustrating two different embodiments ofmobile stations according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows part of a mobile communication system 10, including acellular network and mobile stations, which apart from the normal speechand data communication is capable of transmission of SMS (short messageservice) messages. In the network according to FIG. 1 there are twomobile switching centers (MSCs) 131 and 132, each MSC is connected to acorresponding radio base station (RBS) 121 and 122. A sending mobilestation 101 intends to transmit a message to a receiving mobile station102, via the respective MSCs 131 and 132. For this purpose, there arealso in the system two message centers 141 and 142 corresponding to theMSCs 131 and 132, in which messages are stored before a message isdelivered to a recipient, e.g. the receiving mobile station 102.

In general a network, such as a cellular network conforming to theTIA/EIA-136 and TIA/EIA-41 specification, is composed of a plurality ofareas, each area being served by an MSC having an integrated visitorlocation register (VLR), see MSC/VLR 131 and 132 in FIG. 1. The MSC/VLRareas, in turn, include a plurality of location areas (LAs), which aredefined as a part of a given MSC/VLR area in which a mobile station maymove freely without having to send update location information to theMSC/VLR that controls the location area. Each location area is dividedinto a number of cells.

The RBS is the physical equipment, illustrated for simplicity as a radiotower 121 and 122 in FIG. 1, that provides radio coverage to the cell itis serving.

The VLR is a database containing information about all of the mobilestations currently located within the MSC/VLR area. If a mobile stationroams into a new MSC/VLR area, the VLR connected to that MSC willrequest data about that mobile station from the home location register(HLR) database 150, simultaneously informing the HLR 150 about thecurrent location of the mobile station. Accordingly, if the user of themobile station then wants to make a call, the local VLR will have therequisite identification information without having to reinterrogate theHLR 150. In the aforedescribed manner, the VLR and HLR 150 databases,respectively, contain various subscriber informations associated with agiven mobile station.

The HLR 150 maintains all subscriber information, e.g., user profiles,current location information, international mobile subscriber identity(IMSI) numbers, and other administrative information. It may beco-located with a given MSC, integrated with the MSC, or alternativelyservice multiple MSCs, the latter of which is illustrated in FIG. 1.

FIG. 2 is an overview of the layer 2 subchannels of the Digital ControlChannel (DCCH) and Digital Traffic Channel (DTC) used in the presentsystem and also for the SMS service as shown in FIG. 1.

The layer 2 functionality supported in TIA/EIA-136 reflects theoperational requirements of the subchannels that make up the DCCH andthe DTC. As a result of the differences in subchannel requirements,distinct layer 2 protocols have been specified for the major subchannelgroupings as shown in FIG. 2.

The SPACH logical channel in DCCH is used to broadcast information tospecific mobile stations regarding SMS Point-to-Point (SMSCH), paging(PCH) and to provide an access response channel (ARCH).

On the DTC, the logical channels that are used for SMS transport can beeither the FACCH (Fast Associated Control Channel) or the SACCH (SlowAssociated Control Channel).

A teleservice message, such as a SMS DELIVER or SMS SUBMIT messageincluding a SMS message is delivered across the TIA/EIA-136 airinterface on a DCCH or DTC inside a layer 3 R-DATA message, and acrossthe TIA/EIA-41 network interface inside a layer 3 Short Message DeliveryPoint-to-Point SMDPP Invoke message (see FIG. 3). The delivery of thelayer 3 message may be acknowledged by the destination in a TIA/EIA-136R-DATA ACCEPT or R-DATA REJECT message and a TIA/EIA-41 SMDPP ReturnResult message (see FIG. 3).

In describing how an SMS message is sent from a sending mobile station101 to a receiving mobile station 102 (in FIG. 1), sending mobilestation 101 first establishes a connection to the network (servingMSC/VLR 131), via an allocated digital control channel (DCCH. However,it should be noted that if sending mobile station 101 is in busy mode(in use), a connection already exists and the SMS message will betransmitted on the digital traffic channel (DTC) already in use for theexisting call. It is also possible to set up a DTC specifically just tosend and SMS. MSC/VLR 131 corresponding to the sending mobile station101, transmits the message to the sending mobile station's messagecenter 141. Thereafter, this message center 141 sends the message to thereceiving mobile station's message center 142. Then the receivingmobile's message center 142 asks the HLR for routing informationregarding the receiving mobile station 102. The HLR returns routinginformation to the receiving mobile's message center 142, which thenroutes the message to the MSC/VLR 132. The mobile station 102 is pagedin that MSC/VLR-area, a connection is set-up between the network and themobile station 102, and the message is sent from the network to themobile station 102.

As a person skilled in the art appreciates, a single message center 141or 142, in FIG. 1, may serve both sending and receiving mobile stations101 and 102, as long as the mobile stations belong to the same messagecenter. It is in no way limited to be different message centers 141 or142 for different mobile stations 101 and 102, as described in thesection above.

The MSC provides the interworking between the message center and themobile station by translating between the TIA/EIA-136 and TIA/EIA-41protocols.

If the delivery was unsuccessful, e.g. because the receiving mobilestation 102 was switched off, a messages waiting service within themessage center 142 can optionally provide the HLR and the servingMSC/VLR 132 with the information that there is a message in the messagecenter 142 waiting to be delivered to the receiving mobile station 102.Once the receiving mobile station 102 becomes available for receipt ofthe SMS message, the HLR 150 informs the message center 142 and the SMSmessage is sent again.

An example message flow for SMS sent from one mobile station to anothermobile station is illustrated in FIG. 3. The SMS message from sendingmobile station 101 is encapsulated into the User Data Unit of the SMSSUBMIT message. The SMS SUBMIT message is delivered to the cellularnetwork in an R-DATA message on either the DCCH or the DTC in FIG. 2.The R-DATA message, in FIG. 4, is translated into an SMDPP Invokemessage by the MSC 131 serving sending mobile station 101 and deliveredto the message center 141 serving sending mobile station 101. Themessage center 141 serving sending mobile station 101 sends anacknowledgement in the form of an SMDPP Return Result message to the MSC131. The MSC 131 in turn sends out an R-DATA ACCEPT message to thesending mobile station 101 to indicate that the message has beenreceived by the MSC 131. The message center 141 serving sending mobilestation 101 routes the SMS message to the message center 142 in an SMDPPInvoke message. The message center 142 acknowledges the received SMDPPInvoke message with a SMDPP Return Result message to the message center141 serving sending mobile station 101. An SMDPP Invoke messagecontaining the SMS message for receiving mobile station 102 in an SMSDELIVER message is sent to an MSC 132 serving receiving mobile station102 by the message center 142. The MSC 132 then translates the SMDPPInvoke message into a R-DATA message and sends it to receiving mobilestation 102 which in turn acknowledges the receipt of the R-DATA messagewith an R-DATA ACCEPT. The MSC 132 then sends an SMDPP Return Resultmessage to the message center 142 as an acknowledgement of the SMSmessage delivery to receiving mobile station 102. This step completesthe routing of the SMS message from mobile station 101 to mobile station102 through the R-DATA and SMDPP Invoke messages.

The sender of a SMS message can today associate the message with avalidity period 610 (see FIG. 6) that in that case will be transferredin a validity period field 610 in the SMS SUBMIT message to the messagecenter 141/142. In the message center 142 the SMS message will bedeleted if the message is not delivered within the validity period 610to the receiving mobile station 102. The reason why a SMS message maynot be delivered in time could e.g., be that the receiving mobilestation 102 is turned off.

One scenario is that a message 611 (see FIG. 6) that has been deliveredto the receiving mobile station 102 becomes overdue and still remains inthe receiver's mobile station first memory 601. For someone thatreceives several messages a day, having useless messages stored inhis/her mobile station 102 is inconvenient. It might result in that someimportant messages in the first memory 601 needs to be erased due tolack of space in memory when a new message is received or that the newmessage is never saved. Therefore, important messages may never be savedor older interesting messages may be deleted before they have been read.

The present invention enables a more flexible way of processing amessage at a receiving mobile station 102. In order to properly manageoverdue messages, it is important to determine when they are overdue.This is possible if the validity period 610, set by the sender 101 andused in the message center 141/142, is passed to the receiving mobilestation 102.

With a validity period field 401 included in the SMS DELIVER messagetogether with SMS message (see FIG. 4), the validity period 610information can be accessed in the receiving mobile station 102 and theuser of the receiving mobile station 102 can use the information todecide if messages are overdue, and take actions on overdue messages.The user of the mobile station 102 can choose for example to deleteoverdue messages or to keep them in or forward them to a second memory602/603. The messages 611 may be time specific, but the user of a mobilestation 102 may anyway choose to keep a message 611 instead of deletingit or he/she may choose to delete a message 611 after a grace period.The user could further choose e.g. whether messages 611 should beconditionally erased to allow for the reception of higher prioritymessages or whether they should be erased, as soon as their validityperiod 610 is up. Another choice could be to forward the message 611 toa digital calendar 620 or another kind of storage 602/603 depending onthe validity period 610.

According to one exemplary embodiment of the invention in a method fortransmitting a message in a mobile communication system 10 from aoriginating party 101 to a receiving mobile station 102 the message 611is first transmitted from the originating party 101 to a message center141/142 where it is stored. Further, both the message 611 and associatedvalidity period 610, are transmitted from the message center 141/142 tothe receiving mobile station 102, and associated validity period 610 isbeing used in the receiving mobile station 102.

In this exemplary embodiment of a method according to the invention, thefield validity period 610 in the SMS SUBMIT message will correspond to anew field validity period 401 of the SMS DELIVER message when the SMSmessage is transferred from the message center 141/142 to the receivingmobile station 102. Included in the SMS DELIVER message is also otherfields of information elements (such as Message Type Indicator, MessageReference etc., see FIG. 4) plus the SMS message 611 included in theUser Data Unit 402 (see TIA/EIA-136). The receiver can choose to dealwith SMS messages that are forwarded to the receiving mobile station 102in his/her way by using the validity period 610 sent in the validityperiod field 401.

The message center 141/142 is today deleting all SMS messages in themessage center, which according to the validity period 610 are overdue.According to one alternative embodiment of the invention the SMSmessages that become overdue when in the message center may instead ofbeing deleted be transmitted to their destination regardless of theirassociated validity periods. This implies the choice of how to processthe message is totally up to the receiver of the message, if he/shelikes to use the information in the validity period field 610 or not. Itcan of course be optional to let the message center 141/142 deletemessages that are overdue according to the validity period 610 or totransmit them regardless. If they are overdue or not the messagestransmitted in time to the receiving mobile station 102 can still beprocessed, in accordance with the preferences set by the user of thereceiving mobile station 102.

In the future it may be possible to include a validity period 610 alsoin SMS messages 611 originating from a WEB-page on the Internet or ine-mails converted to SMS messages.

The validity period 610 is provided in the validity period field 401 ineither offset or integer form. In the first case, the validity periodfield 401 provides the length of the validity period 610, counted fromwhen the SMS SUBMIT message is received by the message center 141/142.In the second case, the validity period 610 provides the absolute dateand/or time of the validity period 610 termination. A Validity PeriodFormat field indicates the format used to code the validity period 610.

How many alphanumeric characters that are allowed in a short messageservice (SMS) is limited by the message center that may have differentmaximum message length capability. The maximum message length isdependent on the implementation and can also be set by the systemoperators to optimize the system performance.

FIG. 4 illustrates generally the transmission protocol when sendingR-DATA message according to the TIA/EIA-136 standard and how an SMSDELIVER message is created and transmitted as part of an R-DATA Unit 406which in turn is part of an R-DATA message. The format of the R-DATAmessage is generally described in the TIA/EIA-136-123B 5.3.11.

The R-DATA Unit 406 comprises a Length Indicator 403, a Higher LayerProtocol Identifier 404 and a Higher Layer Protocol Data Unit 405. ThisData Unit 405 includes the SMS DELIVER message. The SMS DELIVER messagecomprises a number of information elements including an User Data Unitfield 402, containing the SMS message 611, being transmitted, a newValidity Period field 401, containing a validity period 610 associatedwith said SMS message 611.

FIG. 5 shows a flow chart of how an SMS message 611 and an associatedvalidity period 610 are received and manipulated in the receiving mobilestation in accordance with the receiver's preferences.

Once the user of the receiving mobile station 102 turns on 501 thereceiving mobile station 102 he/she might enter preferences 502 such aswhether a received message 611 should be stored in a first memory 601until the associated validity period has expired, whether the user ofthe receiving mobile station 102 should be notified when the associatedvalidity period 610 of a message 611 in the first memory 601 expires,whether the received message and the associated validity period 610should be transferred 604/605 to a second memory 602/603, or deletedfrom the first memory 601 when the associated validity period 610expires. The user of a receiving mobile station 102 might also specifywhether a grace period should apply before the message is deleted fromthe first memory 601 and whether messages that are overdue (messageswith an expired associated validity period 610) should be placed in asecond memory 602 included in the receiving mobile station 102 orexternal 603 to the receiving mobile station 102.

Thus, when a message arrives 503, the message 611 and associatedvalidity period 610 are stored 504 in a first memory 601 in thereceiving mobile station 102. The receiving mobile station 102 extractsthe associated validity period 610 if there is one provided andinitiates a time supervision for that message by for example setting 505a timer 606 in accordance with the associated validity period 610. Whenthe timer expires (an alternative Yes at 506), the receiving mobilestation 102 uses 507 the preferences set by the user of the receivingmobile 102 in order to determine whether for example the messages shouldbe deleted 508 in first memory 601 or transferred 604/605 to a secondmemory 602/603 and deleted 508 from the first memory 601. In additionthe receiving mobile station 102 might provide the user with the statusof transferred and deleted messages by displaying 510 a suitable icon onits screen 607. The receiving mobile station 102 can include anotification function, which would notify the user of the receivingmobile station 102 when the message 611 with an associated validityperiod 610 expires. Alternatively the user of the receiving mobilestation 102 could be notified some time before (set according to userpreferences) the message expires. Depending on how much earlier the userwants to receive a notification. The receiving mobile station 102 shouldbe able to provide a record of messages that have been erased comprisingthe sender's address, the validity period 610 and the degree of urgency.

Instead of using a timer 606 the current date and/or time could beregistered when a new message 611 arrives at the receiving mobilestation 102. If the message 611 has an associated validity period 610,said validity period is compared to the registered current date and timeto find out if the validity period 610 has expired.

When the option is set by the user of the receiving mobile station 102to store received new SMS messages 611 in a first memory 601 in thereceiving mobile station 102, it is first necessary to control if thereis enough available memory in the first memory 601 in the receivingmobile station 102 before storing the new received message. In case of ashortage of available memory, validity periods of the earlier storedmessages are checked, and if a message is overdue, the overdue messageis deleted to make space for the newly arrived message (the user of thereceiving mobile station may even get a choice of reading the messagethat is going to be deleted before it is deleted if so is the option).This means that not more messages are deleted than is needed to makespace for the newly received message. It may happen that there aremessages which are not overdue but their validity periods are closer intime to become overdue than the newly arrived message 611 and there arenot enough available memory in the first memory 601 of the receivingmobile station for saving the newly arrived message 611. At thesemoments there are different ways of processing the message such asalways deleting the newly arrived message 611, deleting a message havinga validity period that will expire first, transfer the newly arrivedmessage 611 or the message having a validity period that will expirefirst to a second memory 602/603 etc. The second memory 602/603 can be aseparate second memory 602 inside the receiving mobile station or anexternal separate second memory 603. Another solution is to frequentlycheck the first memory 601 for overdue messages instead of each time anew message arrives. When a check is done in the first memory 601 foroverdue messages, the associated validity period 610 is compared to thedate and/or time when the check is executed. See further what isdescribed above.

In FIG. 6 is a block diagram illustrating two different mobile stations102/620 comprising memories 601/602/603, a timer means 606 and a displaymeans 607. In the receiving mobile station 102 is included at least onefirst memory 601. There may also be a second memory 602, which isseparate from the first memory 601. If the first memory 601 is full canaccording to preferences set by the user of the mobile station 102 themessage 611 and associated validity period 610 be deleted from the firstmemory 601, and/or moved 604 to the second memory 602 inside the samereceiving mobile station 102. The message 611 and associated validityperiod 610 can also be moved 605′ to a second memory 603 included inanother device such as e.g. a digital calendar 620. A receiving mobilestation 102 can also include calendar functions. In one solution to acalendar function described in FIG. 5, is needed a timer means 606 inthe receiving mobile station 102. To display the messages 611 a displaymeans 607 is included in the receiving mobile station 102.

As a person skilled in the art appreciates, application of the inventionis in no way limited to only radio communication systems conforming tothe TIA/EIA-136 and TIA/EIA-41 specifications. The invention is on thecontrary applicable in e.g. all systems which utilizes short messagesservices such as systems conforming to e.g., the GSM-, PDC-, IS-95-,UMTS- or DECT-specifications.

As will be recognized by those skilled in the art, the innovativeconcepts described in the present application can be modified and variedover a wide range of applications. Accordingly, the scope of patentedsubject matter should not be limited to any of the specific exemplaryteachings discussed.

1. A method for transmitting a message in a mobile communication systemfrom an originating party to a receiving mobile station, wherein saidmobile communication system includes a message center, and where avalidity period is associated with said message, comprising the stepsof: receiving a message from said originating party wherein said messageincludes a validity period, transmitting both said message and saidassociated validity period via said message center to said receivingmobile station.
 2. A method according to claim 1, wherein if saidmessage and said associated validity period have not been delivered tosaid receiving mobile station upon expiry of said validity period, themessage is deleted by said message center.
 3. A method according toclaim 1, wherein said message center attempts to transmit said messageand said associated validity period to said receiving mobile stationeven after expiry of said associated validity period.
 4. A methodaccording to claim 1, wherein said message and said associated validityperiod are transmitted in an SMS DELIVER message from said messagecenter to said receiving mobile station.
 5. A method according to claim4, wherein said SMS DELIVER message is transported in a layer 3 R-DATAmessage.
 6. A method according to claim 1, wherein said associatedvalidity period is given in form of an expire time of said message.
 7. Amethod according to claim 1, wherein said associated validity period isgiven in form of an offset time counted from when said message and saidassociated validity period are received by said message center.
 8. Amethod according to claim 1, wherein after receipt of said message bysaid receiving mobile station, said message is processed according topredetermined rules and said validity period.
 9. A method according toclaim 8, wherein said predetermined rules are based on preferences setby a user of said receiving mobile station.
 10. A method according toclaim 9, wherein in accordance with said predetermined rules, saidassociated validity period is read and a time supervision is initiatedin accordance with said associated validity period.
 11. A methodaccording to claim 10, wherein in accordance with said predeterminedrules, said message and said associated validity period are transferredfrom a first memory to a second memory when said associated validityperiod has expired.
 12. A method according to claim 10, wherein inaccordance with said predetermined rules, said message and saidassociated validity period are deleted from a first memory when saidassociated validity period has expired.
 13. A method according to claim12, wherein a grace period is applied, before said message and saidassociated validity period are deleted from said first memory.
 14. Amobile station comprising: means for receiving a message wherein saidmessage includes an associated validity period, and a first memory forstoring said message and said associated validity period until saidassociated validity period has expired.
 15. A mobile station accordingto claim 14, wherein said mobile station further comprises a secondmemory, said message and said associated validity period are transferredfrom said first memory to said second memory when said associatedvalidity period has expired.
 16. A mobile station claim 14, wherein saidmessage and said associated validity period are deleted from said firstmemory when said associated validity period has expired.
 17. A mobilestation according to claim 16, wherein a grace period is applied, beforesaid message and said associated validity period are deleted from saidfirst memory.